feat(client/orders): 订单列表/详情显示 expired 过期态

- _statusPill 函数加 'expired' => neutral 灰状态胶囊(复用 canceled 视觉档)
- actions() 函数让 expired 单复用 created 分支,显示「继续支付」按钮
- 对接后端 Task 0 返回的 status=='expired' + Task 2 的 t.orderStatusExpired

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/lib/screens/orders_page.dart

@@ -35,12 +35,13 @@ String _methodName(AppText t, String method) => switch (method) {
       _ => method,
     };
 
-/// 订单状态 → (胶囊色, 文案)。created=等待付款 / paid=已开通 / canceled=已取消。
+/// 订单状态 → (胶囊色, 文案)。created=等待付款 / paid=已开通 / canceled=已取消 / expired=已过期。
 ({PangolinStatus status, String label}) _statusPill(AppText t, String status) =>
     switch (status) {
       'created' => (status: PangolinStatus.connecting, label: t.awaitingPayment),
       'paid' => (status: PangolinStatus.connected, label: t.orderStatusPaid),
       'canceled' => (status: PangolinStatus.neutral, label: t.orderStatusCanceled),
+      'expired' => (status: PangolinStatus.neutral, label: t.orderStatusExpired),
       _ => (status: PangolinStatus.neutral, label: status),
     };
 
@@ -327,6 +328,7 @@ class _OrderDetailView extends ConsumerWidget {
       final list = <Widget>[];
       switch (o.status) {
         case 'created':
+        case 'expired':
           list.add(PangolinButton(label: t.orderContinuePay, expand: true, onPressed: () => _goPurchase(context, ref)));
         case 'canceled':
           list.add(PangolinButton(label: t.orderRebuy, expand: true, onPressed: () => _goPurchase(context, ref)));